GEOTHERMAL MAPPING USING TEMPERATURE MEASUREMENTS By Godwin Mwawongo Reservoir Engineer
GEOTHERMAL MAPPING
USING TEMPERATURE
MEASUREMENTS
By
Godwin Mwawongo
Reservoir Engineer
Introduction-Geo systems
• Mostly located close to active
tectonic plates
• Tectonic activity results in faulting
• Hot rocks are brought close to the
surface
• Water seeps through deep faults
• Hot rocks heat the water
• Pressure builds up
• Faults provide leakage paths
• Heat loss features are formed in
the leakage areas
• Hot springs, fumeroles, hot
grounds are heat loss features
Heat loss mechanism
• Heat loss features continuously transfer heat
and mass from the geothermal system to the
atmosphere
• Heat transfer is by:
–conduction
–convection
–Radiation
• Estimate amount of heat being lost naturally
• Analyze distribution of heat loss features
• Ranking geothermal prospects for development
• Results obtained can be used as an indicator of the
heat source size
• Give an indication of the magnitude of recharge
• Indicates extent of leakage through the capping.
• Assist in locating hidden fracture zones.
Objectives of heat loss survey
Measurements in boreholes
• Down hole temperature measurement
– Bore holes serve as temperature gradient holes
– Results can be used to estimate temperatures at depth
• Down hole pressure measurements
– Assist in modeling hydrological picture of the prospect
– Give an indication of possible recharge and outflow zones.
•14 geothermal prospects in
Kenya
•Estimated power potential is
over 3000 MWe
•Geothermal Resource
Assessment (GRA) was
formed to fast track
geothermal power
development
•From 2004 to 2007 studies
have been conducted from
Menengai to Paka
•Heat flow measurements
included.
Geothermal Prospects in Kenya
Menengai-Olbanita Prospect
• Associated with a 90 km2
Menengai Caldera
• Heat flow survey covered an area of about 900 km2.
• Heat loss features are mainly hot grounds & fumeroles
Menengai
Olbanita
180170160
9990
9980
9970
2200
2 100
200 0
1900
1800
1700
160
0
1700
180 0
1 800
2000
1900
2000
18001 8
00 1 800
1 800
1800
1800
18 00
1900
2000
2100
2 160
21
00
2200
200
0
2000
210
0
2000
19 00
180 0
1900
19 00
1900
2000
200 0
210
0
2200
2300
2200
1800
170
0
1700
18
00
1800
1800
1700
1700
1600
1700
2000 2200
2200
L. NAKURU
NAKURU TOWN LANET
R . N j or o
KIA
MU
NYI
ES
TAT
E
NGATA FARM
M E NE N GA I S TAT IO N
KABARAK ESTATE
CALDERAENGOSHURA FARM
KABATINICrater stream
BAHATI
SOLAI
BANITASISAL ESTATE
OLBANITA SWAMP & POND
Olba
nita s
tream
kabaragi
KISANANA
MAJANI MINGI ESTATE
ATHINAI SISAL ESTATE
EL BONWALA
OL' R
ON
GA
I HIL
LS
MENEGAI HILL FARM
KAMPIYA MOTO
MOGOTIO
0 10KMLEGEND
200
0Contours in meters above sea level
Roads
Railway line
Rivers
Lake, Pond
Shoppingcenter
Pyroclastic issuecrates
Lava eruption center
Major (r ift scarp) fault
Rift floorfault
Inferred fault
00
II
Borehole
FumarolesProposed exploration well site
MW-1
MW-3MW-2
MW-3
MENENGAI
40
50
60
70
80
Menengai-Olbanita, cont• Orientation of heat loss
features is NNW-SSE and
NE-SW
• Total conductive heat loss
is 1060 MWt
• Total convective heat loss
is 2476 MWt
• This indicates large heat
source for the prospect
Arus-Bogoria Prospect
Arus &
Lake Bogoria • Not associated with a
central volcano
• Heat loss features are hot
springs, geysers, hot
grounds & steam jets
Arus steam jet
Geyser at
L Bogoria
Arus
Bogoria
Arus and Lake Bogoria, cont
• Total heat loss from
the two prospects is
1666 MWt
• Orientation of the
features is NE-SW
at Arus and NW-SE
at Bogoria
Lake Baringo Prospect
• Lake Baringo covers a
large part of this
prospect thus, reducing
the effective area
substantially
• Thick alluvial deposits
lowers natural heat loss
as it acts as an
insulator
• Has no central volcano
Lake Baringo
Lake Baringo prospect, cont
• Anomalous bore holes
have been drilled in this
prospect
• A 90 m bore hole
discharging boiling water.
• Heat loss features are
hot grounds and
fumeroles
Lake Baringo Prospect, cont
Eastings
Tanglubei
Paoyi
Riongo
Loruk
Chesirimion
Chemiril
Kadogoi
Cepkalacha
Komolion
1
2
3
45
6 78
9
10
11
12
13
14
15
16
1718
19
2021
L Baringo
OlKokweisland
°C
Legend
Craters
Contours
Roads
Paka Craters
Lake Tulam
0 42Kilometers
162000 166000 170000 174000 178000 182000 186000 190000 194000 198000
Piezometric Level
CentersBorehole
Temp GradientContour
40
50
60
70
80
Lake Baringo
prospect
• Orientation of heat
loss features is
NW-SE
• Total heat loss
from the prospect
is > 1049 MWt
Korosi and Chepchuk
• Korosi is a central
volcano
• Extends to the North of
Lake Baringo prospect
• Hot grounds and
fumeroles cover about 45
km2
Korosi &
Chepchuk
Eastings
Tanglubei
Paoyi
Riongo
Loruk
Chesirimion
Chemiril
Kadogoi
Cepkalacha
Komolion
1
2
3
45
6 78
9
10
11
12
13
14
15
16
1718
19
2021
L Baringo
OlKokweisland
°C
Legend
Craters
Contours
Roads
Paka Craters
Lake Tulam
0 42Kilometers
162000 166000 170000 174000 178000 182000 186000 190000 194000 198000
Piezometric Level
CentersBorehole
Temp GradientContour
40
50
60
70
80
Korosi and Chepchuk, cont
• Heat loss features at
Korosi are controlled
by NE-SW and NW-
SE trending faults.
Conduction
– About 2,135 MWt
Korosi
– About 546 MW at
Chepchuk.
Convection
• 0.4 kWt
Lake Baringo
Chepchuk
Korosi
Paka prospect, cont
• Associated with a central
volcano
• Study covered 500 km2
• Heat loss features are hot
grounds, fumeroles
steaming grounds
• Located in & around the
caldera
Heat loss features cover 32
km2
Max. temperature 93oC
Paka
Paka prospect, cont• Heat loss features
display NE-SW
&NW-SE trend
• Conductive heat
loss is 2,655 MWt
• Convective heat
loss is 10 MWtLake Baringo
Eastings
Tanglubei
Paoyi
Riongo
Loruk
Chesirimion
Chemiril
Kadogoi
Cepkalacha
Komolion
1
2
3
45
6 78
9
10
11
12
13
14
15
16
1718
19
2021
L Baringo
OlKokweisland
40
50
60
70
80
°C
Legend
Craters
Contours
Roads
Paka Craters
Lake Tulam
0 42Kilometers
162000 166000 170000 174000 178000 182000 186000 190000 194000 198000
Temp Gardient Contours
CentersBorehole
Paka
Korosi &
Chepchuk
Temperature & hydraulic
gradient
• Bore holes indicate
230oC/m near the
active zones of the
prospects
• Cold areas indicate
0.02oC/m
• Water flow is from east
& west and from south
to north
Eastings
Tanglubei
Paoyi
Riongo
Loruk
Chesirimion
Chemiril
Kadogoi
Cepkalacha
Komolion
1
2
3
45
6 78
9
10
11
12
13
14
15
16
1718
19
2021
L Baringo
OlKokweisland
40
50
60
70
80
°C
Legend
Craters
Contours
Roads
Paka Craters
Lake Tulam
0 42Kilometers
162000 166000 170000 174000 178000 182000 186000 190000 194000 198000
Piezometric Level
CentersBorehole
Temp GradientContour
Paka
Korosi
Baringo
Chepchuk
Ranking based on heat lossProspect Heat loss Total heat loss
(MWt)Conductive
(MWt)
Convective
(MWt)
Menengai 1095 2440 3536
Paka 2845 10 2855
Korosi 2135 0.4 2135
Bogoria 762 437 1199
Baringo 941 108 1049
Chepchuk 546 Negligible 546
Arus 467 .03 467
Olkaria 400
Domes 187
160 180 200
Eastings (km)
-20
0
20
40
60
80
100
Nort
hin
gs (
km
)
40
50
60
70
80
°C
PakaCaldera
ChepchukKorosi
L Baringo
L Bogoria
Arus
Ol Banita
MenengaiCaldera
KinyachCrater
Equator
Paka Prospect
Menengai Prospect
Menengai to Paka
• Heat loss features display
NW-SE and NE-SW trend
• L. Bogoria and L Baringo
heat loss features are
NW-SE
• Korosi heat loss features
are oriented in NE-SW